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<a href="sched__task__fwd_8hpp.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a id="l00001" name="l00001"></a><span class="lineno">    1</span><span class="comment">/* Flow</span></div>
<div class="line"><a id="l00002" name="l00002"></a><span class="lineno">    2</span><span class="comment"> * Copyright 2023 Akamai Technologies, Inc.</span></div>
<div class="line"><a id="l00003" name="l00003"></a><span class="lineno">    3</span><span class="comment"> *</span></div>
<div class="line"><a id="l00004" name="l00004"></a><span class="lineno">    4</span><span class="comment"> * Licensed under the Apache License, Version 2.0 (the</span></div>
<div class="line"><a id="l00005" name="l00005"></a><span class="lineno">    5</span><span class="comment"> * &quot;License&quot;); you may not use this file except in</span></div>
<div class="line"><a id="l00006" name="l00006"></a><span class="lineno">    6</span><span class="comment"> * compliance with the License.  You may obtain a copy</span></div>
<div class="line"><a id="l00007" name="l00007"></a><span class="lineno">    7</span><span class="comment"> * of the License at</span></div>
<div class="line"><a id="l00008" name="l00008"></a><span class="lineno">    8</span><span class="comment"> *</span></div>
<div class="line"><a id="l00009" name="l00009"></a><span class="lineno">    9</span><span class="comment"> *   https://www.apache.org/licenses/LICENSE-2.0</span></div>
<div class="line"><a id="l00010" name="l00010"></a><span class="lineno">   10</span><span class="comment"> *</span></div>
<div class="line"><a id="l00011" name="l00011"></a><span class="lineno">   11</span><span class="comment"> * Unless required by applicable law or agreed to in</span></div>
<div class="line"><a id="l00012" name="l00012"></a><span class="lineno">   12</span><span class="comment"> * writing, software distributed under the License is</span></div>
<div class="line"><a id="l00013" name="l00013"></a><span class="lineno">   13</span><span class="comment"> * distributed on an &quot;AS IS&quot; BASIS, WITHOUT WARRANTIES OR</span></div>
<div class="line"><a id="l00014" name="l00014"></a><span class="lineno">   14</span><span class="comment"> * CONDITIONS OF ANY KIND, either express or implied.</span></div>
<div class="line"><a id="l00015" name="l00015"></a><span class="lineno">   15</span><span class="comment"> * See the License for the specific language governing</span></div>
<div class="line"><a id="l00016" name="l00016"></a><span class="lineno">   16</span><span class="comment"> * permissions and limitations under the License. */</span></div>
<div class="line"><a id="l00017" name="l00017"></a><span class="lineno">   17</span><span class="comment"></span> </div>
<div class="line"><a id="l00018" name="l00018"></a><span class="lineno">   18</span><span class="comment">/// @file</span></div>
<div class="line"><a id="l00019" name="l00019"></a><span class="lineno">   19</span><span class="comment"></span><span class="preprocessor">#pragma once</span></div>
<div class="line"><a id="l00020" name="l00020"></a><span class="lineno">   20</span> </div>
<div class="line"><a id="l00021" name="l00021"></a><span class="lineno">   21</span><span class="preprocessor">#include &quot;<a class="code" href="util__fwd_8hpp.html">flow/util/util_fwd.hpp</a>&quot;</span></div>
<div class="line"><a id="l00022" name="l00022"></a><span class="lineno">   22</span><span class="preprocessor">#include &quot;<a class="code" href="log__fwd_8hpp.html">flow/log/log_fwd.hpp</a>&quot;</span></div>
<div class="line"><a id="l00023" name="l00023"></a><span class="lineno">   23</span><span class="preprocessor">#include &lt;boost/shared_ptr.hpp&gt;</span></div>
<div class="line"><a id="l00024" name="l00024"></a><span class="lineno">   24</span> </div>
<div class="line"><a id="l00025" name="l00025"></a><span class="lineno">   25</span><span class="keyword">namespace </span><a class="code hl_namespace" href="namespaceflow_1_1util.html">flow::util</a></div>
<div class="line"><a id="l00026" name="l00026"></a><span class="lineno">   26</span>{</div>
<div class="line"><a id="l00027" name="l00027"></a><span class="lineno">   27</span> </div>
<div class="line"><a id="l00028" name="l00028"></a><span class="lineno">   28</span><span class="comment">// Types.</span></div>
<div class="line"><a id="l00029" name="l00029"></a><span class="lineno">   29</span> </div>
<div class="line"><a id="l00030" name="l00030"></a><span class="lineno">   30</span><span class="comment">// Find doc headers near the bodies of these compound types.</span></div>
<div class="line"><a id="l00031" name="l00031"></a><span class="lineno">   31</span> </div>
<div class="line"><a id="l00032" name="l00032"></a><span class="lineno">   32</span><span class="keyword">struct </span>Scheduled_task_handle_state;</div>
<div class="line"><a id="l00033" name="l00033"></a><span class="lineno">   33</span><span class="comment"></span> </div>
<div class="line"><a id="l00034" name="l00034"></a><span class="lineno">   34</span><span class="comment">/**</span></div>
<div class="line"><a id="l00035" name="l00035"></a><span class="lineno">   35</span><span class="comment"> * Black-box type that represents a handle to a scheduled task as scheduled by</span></div>
<div class="line"><a id="l00036" name="l00036"></a><span class="lineno">   36</span><span class="comment"> * schedule_task_at() or schedule_task_from_now() or similar, which can be (optionally) used to control the</span></div>
<div class="line"><a id="l00037" name="l00037"></a><span class="lineno">   37</span><span class="comment"> * scheduled task after it has been thus scheduled.  Special value `Scheduled_task_handle()` represents an invalid task</span></div>
<div class="line"><a id="l00038" name="l00038"></a><span class="lineno">   38</span><span class="comment"> * and can be used as a sentinel, as with a null pointer.</span></div>
<div class="line"><a id="l00039" name="l00039"></a><span class="lineno">   39</span><span class="comment"> *</span></div>
<div class="line"><a id="l00040" name="l00040"></a><span class="lineno">   40</span><span class="comment"> * Values of this type are to be passed around by value, not reference.  They are light-weight.</span></div>
<div class="line"><a id="l00041" name="l00041"></a><span class="lineno">   41</span><span class="comment"> * Officially, passing it by reference results in undefined</span></div>
<div class="line"><a id="l00042" name="l00042"></a><span class="lineno">   42</span><span class="comment"> * behavior.  Unofficially, it will probably work (just haven&#39;t thought super-hard about it to make sure) but will</span></div>
<div class="line"><a id="l00043" name="l00043"></a><span class="lineno">   43</span><span class="comment"> * bring no performance benefit.</span></div>
<div class="line"><a id="l00044" name="l00044"></a><span class="lineno">   44</span><span class="comment"> */</span></div>
<div class="line"><a id="l00045" name="l00045"></a><span class="lineno"><a class="line" href="namespaceflow_1_1util.html#aa0d10f5a906b3229f48979aa43e9ff7e">   45</a></span><span class="keyword">using </span><a class="code hl_typedef" href="namespaceflow_1_1util.html#aa0d10f5a906b3229f48979aa43e9ff7e">Scheduled_task_handle</a> = boost::shared_ptr&lt;Scheduled_task_handle_state&gt;;</div>
<div class="line"><a id="l00046" name="l00046"></a><span class="lineno">   46</span><span class="comment"></span> </div>
<div class="line"><a id="l00047" name="l00047"></a><span class="lineno">   47</span><span class="comment">/**</span></div>
<div class="line"><a id="l00048" name="l00048"></a><span class="lineno">   48</span><span class="comment"> * Equivalent to `Scheduled_task_handle` but refers to immutable version of a task.</span></div>
<div class="line"><a id="l00049" name="l00049"></a><span class="lineno">   49</span><span class="comment"> * One can safely construct a `Scheduled_task_const_handle` directly from `Scheduled_task_handle` (but not vice versa;</span></div>
<div class="line"><a id="l00050" name="l00050"></a><span class="lineno">   50</span><span class="comment"> * nor would that compile without some kind of frowned-upon `const_cast` or equivalent).</span></div>
<div class="line"><a id="l00051" name="l00051"></a><span class="lineno">   51</span><span class="comment"> */</span></div>
<div class="line"><a id="l00052" name="l00052"></a><span class="lineno"><a class="line" href="namespaceflow_1_1util.html#add471ec4a0f0b76793c9c84adb4916d5">   52</a></span><span class="keyword">using </span><a class="code hl_typedef" href="namespaceflow_1_1util.html#add471ec4a0f0b76793c9c84adb4916d5">Scheduled_task_const_handle</a> = boost::shared_ptr&lt;const Scheduled_task_handle_state&gt;;</div>
<div class="line"><a id="l00053" name="l00053"></a><span class="lineno">   53</span><span class="comment"></span> </div>
<div class="line"><a id="l00054" name="l00054"></a><span class="lineno">   54</span><span class="comment">/**</span></div>
<div class="line"><a id="l00055" name="l00055"></a><span class="lineno">   55</span><span class="comment"> * Short-hand for tasks that can be scheduled/fired by schedule_task_from_now() and similar.  `short_fire` shall be</span></div>
<div class="line"><a id="l00056" name="l00056"></a><span class="lineno">   56</span><span class="comment"> * set to `false` if the task executed based on its scheduled time; `true` if it is fired early due to</span></div>
<div class="line"><a id="l00057" name="l00057"></a><span class="lineno">   57</span><span class="comment"> * scheduled_task_short_fire().</span></div>
<div class="line"><a id="l00058" name="l00058"></a><span class="lineno">   58</span><span class="comment"> */</span></div>
<div class="line"><a id="l00059" name="l00059"></a><span class="lineno"><a class="line" href="namespaceflow_1_1util.html#aafa03984c5012ef7db2e7d01b6909a83">   59</a></span><span class="keyword">using </span><a class="code hl_class" href="classflow_1_1Function.html">Scheduled_task</a> = <a class="code hl_class" href="classflow_1_1Function.html">Function</a>&lt;void (<span class="keywordtype">bool</span> short_fire)&gt;;</div>
<div class="line"><a id="l00060" name="l00060"></a><span class="lineno">   60</span> </div>
<div class="line"><a id="l00061" name="l00061"></a><span class="lineno">   61</span><span class="comment">// Free functions.</span></div>
<div class="line"><a id="l00062" name="l00062"></a><span class="lineno">   62</span><span class="comment"></span> </div>
<div class="line"><a id="l00063" name="l00063"></a><span class="lineno">   63</span><span class="comment">/**</span></div>
<div class="line"><a id="l00064" name="l00064"></a><span class="lineno">   64</span><span class="comment"> * Schedule the given function to execute in a certain amount of time: A handy wrapper around #Timer (asio&#39;s timer</span></div>
<div class="line"><a id="l00065" name="l00065"></a><span class="lineno">   65</span><span class="comment"> * facility).  Compared to using #Timer, this has far simplified semantics at the cost of certain</span></div>
<div class="line"><a id="l00066" name="l00066"></a><span class="lineno">   66</span><span class="comment"> * less-used features of #Timer.  Recommend using this facility when sufficient; otherwise use #Timer directly.</span></div>
<div class="line"><a id="l00067" name="l00067"></a><span class="lineno">   67</span><span class="comment"> * The trade-offs are explained below, but first:</span></div>
<div class="line"><a id="l00068" name="l00068"></a><span class="lineno">   68</span><span class="comment"> *</span></div>
<div class="line"><a id="l00069" name="l00069"></a><span class="lineno">   69</span><span class="comment"> * ### Semantics ###</span></div>
<div class="line"><a id="l00070" name="l00070"></a><span class="lineno">   70</span><span class="comment"> * Conceptually this is similar to JavaScript&#39;s ubiquitous (albeit single-threaded) `setTimeout()` feature.</span></div>
<div class="line"><a id="l00071" name="l00071"></a><span class="lineno">   71</span><span class="comment"> * The given function shall execute as if `post()`ed onto the given `Task_engine`; unless successfully canceled by</span></div>
<div class="line"><a id="l00072" name="l00072"></a><span class="lineno">   72</span><span class="comment"> * `scheduled_task_cancel(X)`, where X is the (optionally used and entirely ignorable) returned handle.  Barring</span></div>
<div class="line"><a id="l00073" name="l00073"></a><span class="lineno">   73</span><span class="comment"> * unrelated crashes/etc. there are exactly three mutually exclusive outcomes of this function executing:</span></div>
<div class="line"><a id="l00074" name="l00074"></a><span class="lineno">   74</span><span class="comment"> *   - It runs at the scheduled time, with the `bool short_fire` arg to it set to `false`.</span></div>
<div class="line"><a id="l00075" name="l00075"></a><span class="lineno">   75</span><span class="comment"> *   - It runs before the scheduled time, with `short_fire == true`.  To trigger this, use scheduled_task_short_fire()</span></div>
<div class="line"><a id="l00076" name="l00076"></a><span class="lineno">   76</span><span class="comment"> *     before the scheduled time.</span></div>
<div class="line"><a id="l00077" name="l00077"></a><span class="lineno">   77</span><span class="comment"> *     - If this loses the race with normal firing, the short-fire function will indicate that via its return value.</span></div>
<div class="line"><a id="l00078" name="l00078"></a><span class="lineno">   78</span><span class="comment"> *   - It never runs.  To trigger this, use scheduled_task_cancel() before the scheduled time.</span></div>
<div class="line"><a id="l00079" name="l00079"></a><span class="lineno">   79</span><span class="comment"> *     - If this loses the race with normal firing, the cancel function will indicate that via its return value.</span></div>
<div class="line"><a id="l00080" name="l00080"></a><span class="lineno">   80</span><span class="comment"> *</span></div>
<div class="line"><a id="l00081" name="l00081"></a><span class="lineno">   81</span><span class="comment"> * All related functions are thread-safe w/r/t a given returned `Scheduled_task_handle`, if `single_threaded == false`.</span></div>
<div class="line"><a id="l00082" name="l00082"></a><span class="lineno">   82</span><span class="comment"> * In addition, for extra performance (internally, by omitting certain locking),</span></div>
<div class="line"><a id="l00083" name="l00083"></a><span class="lineno">   83</span><span class="comment"> * set `single_threaded = true` only if you can guarantee the following:</span></div>
<div class="line"><a id="l00084" name="l00084"></a><span class="lineno">   84</span><span class="comment"> *   - `*task_engine` is `run()`ning in no more than one thread throughout all work with the returned</span></div>
<div class="line"><a id="l00085" name="l00085"></a><span class="lineno">   85</span><span class="comment"> *     `Scheduled_task_handle` including the present function.</span></div>
<div class="line"><a id="l00086" name="l00086"></a><span class="lineno">   86</span><span class="comment"> *   - Any calls w/r/t the returned `Scheduled_task_handle` are also -- if at all -- called from that one thread.</span></div>
<div class="line"><a id="l00087" name="l00087"></a><span class="lineno">   87</span><span class="comment"> *</span></div>
<div class="line"><a id="l00088" name="l00088"></a><span class="lineno">   88</span><span class="comment"> * The minimum is step 1: Call schedule_task_at() or schedule_task_from_now(). Optionally, if one saves the return</span></div>
<div class="line"><a id="l00089" name="l00089"></a><span class="lineno">   89</span><span class="comment"> * value X from either, one can do step 2: `scheduled_task_short_fire(X)` or `scheduled_task_cancel(X)`, which</span></div>
<div class="line"><a id="l00090" name="l00090"></a><span class="lineno">   90</span><span class="comment"> * will succeed (return `true`) if called sufficiently early.  There is no step 3; any subsequent calls on X</span></div>
<div class="line"><a id="l00091" name="l00091"></a><span class="lineno">   91</span><span class="comment"> * will fail (return `false`).</span></div>
<div class="line"><a id="l00092" name="l00092"></a><span class="lineno">   92</span><span class="comment"> *</span></div>
<div class="line"><a id="l00093" name="l00093"></a><span class="lineno">   93</span><span class="comment"> * ### Simplifications over #Timer ###</span></div>
<div class="line"><a id="l00094" name="l00094"></a><span class="lineno">   94</span><span class="comment"> * - There is no need to, separately, create a #Timer object; set the firing time; and kick off the</span></div>
<div class="line"><a id="l00095" name="l00095"></a><span class="lineno">   95</span><span class="comment"> *   asynchronous wait.  One call does everything, and there is no object to maintain.  Sole exception to the latter:</span></div>
<div class="line"><a id="l00096" name="l00096"></a><span class="lineno">   96</span><span class="comment"> *   *if* you want to be able to cancel or short-circuit the task later on, you can optionally save the return value</span></div>
<div class="line"><a id="l00097" name="l00097"></a><span class="lineno">   97</span><span class="comment"> *   and later call a `scheduled_task_*()` function on it.)</span></div>
<div class="line"><a id="l00098" name="l00098"></a><span class="lineno">   98</span><span class="comment"> * - You need not worry about internal errors -- no need to worry about any `Error_code` passed in to your task</span></div>
<div class="line"><a id="l00099" name="l00099"></a><span class="lineno">   99</span><span class="comment"> *   function.</span></div>
<div class="line"><a id="l00100" name="l00100"></a><span class="lineno">  100</span><span class="comment"> * - Cancellation semantics are straightforward and intuitive, lacking corner cases of vanilla #Timer.  To wit:</span></div>
<div class="line"><a id="l00101" name="l00101"></a><span class="lineno">  101</span><span class="comment"> *   - A successful scheduled_task_cancel() call means the task will *not* execute.  (`Timer::cancel()` means it</span></div>
<div class="line"><a id="l00102" name="l00102"></a><span class="lineno">  102</span><span class="comment"> *     will still execute but with `operation_aborted` code.)</span></div>
<div class="line"><a id="l00103" name="l00103"></a><span class="lineno">  103</span><span class="comment"> *   - `Timer::cancel()` can result in ~3 behaviors: it already executed, so it does nothing; it has not yet executed</span></div>
<div class="line"><a id="l00104" name="l00104"></a><span class="lineno">  104</span><span class="comment"> *     but was JUST about to execute, so it will still execute with non-`operation_aborted` code; it has not yet</span></div>
<div class="line"><a id="l00105" name="l00105"></a><span class="lineno">  105</span><span class="comment"> *     executed, so now it will execute but with `operation_aborted`.  With this facility, it&#39;s simpler:</span></div>
<div class="line"><a id="l00106" name="l00106"></a><span class="lineno">  106</span><span class="comment"> *     it either succeeds (so acts per previous bullet -- does not execute); or it fails, hence it will have executed</span></div>
<div class="line"><a id="l00107" name="l00107"></a><span class="lineno">  107</span><span class="comment"> *     (and there is no `Error_code` to decipher).</span></div>
<div class="line"><a id="l00108" name="l00108"></a><span class="lineno">  108</span><span class="comment"> * - Short-firing semantics are arguably more intuitive.  With #Timer, `cancel()` actually means short-firing</span></div>
<div class="line"><a id="l00109" name="l00109"></a><span class="lineno">  109</span><span class="comment"> *   (firing ASAP) but with a special `Error_code`.  One can also change the expiration time to the past</span></div>
<div class="line"><a id="l00110" name="l00110"></a><span class="lineno">  110</span><span class="comment"> *   to short-fire in a different way.  With this facility, cancellation means it won&#39;t run; and</span></div>
<div class="line"><a id="l00111" name="l00111"></a><span class="lineno">  111</span><span class="comment"> *   scheduled_task_short_fire() means it will fire early; that&#39;s it.</span></div>
<div class="line"><a id="l00112" name="l00112"></a><span class="lineno">  112</span><span class="comment"> *</span></div>
<div class="line"><a id="l00113" name="l00113"></a><span class="lineno">  113</span><span class="comment"> * ### Features lost vs. #Timer ###</span></div>
<div class="line"><a id="l00114" name="l00114"></a><span class="lineno">  114</span><span class="comment"> * - A #Timer can be reused repeatedly.  This *might* be more performant than using this facility repeatedly, since</span></div>
<div class="line"><a id="l00115" name="l00115"></a><span class="lineno">  115</span><span class="comment"> *   (internally) that approach creates a #Timer each time.  Note: We have no data about the cost of initializing a new</span></div>
<div class="line"><a id="l00116" name="l00116"></a><span class="lineno">  116</span><span class="comment"> *   #Timer, other than the fact I peeked at the boost.asio source and saw that the construction of a #Timer isn&#39;t</span></div>
<div class="line"><a id="l00117" name="l00117"></a><span class="lineno">  117</span><span class="comment"> *   obviously trivial/cheap -- which does NOT mean it isn&#39;t just cheap in reality, only that that&#39;s not immediately</span></div>
<div class="line"><a id="l00118" name="l00118"></a><span class="lineno">  118</span><span class="comment"> *   clear.</span></div>
<div class="line"><a id="l00119" name="l00119"></a><span class="lineno">  119</span><span class="comment"> *   - A rule of thumb in answering the question, &#39;Is this facility fine to just call repeatedly, or should we reuse</span></div>
<div class="line"><a id="l00120" name="l00120"></a><span class="lineno">  120</span><span class="comment"> *     a `Timer` for performance?&#39;: It *might* not be fine if and only if timer firings and/or cancellations occur</span></div>
<div class="line"><a id="l00121" name="l00121"></a><span class="lineno">  121</span><span class="comment"> *     many times a second in a performance-sensitive environment.  E.g., if it&#39;s something fired and/or canceled</span></div>
<div class="line"><a id="l00122" name="l00122"></a><span class="lineno">  122</span><span class="comment"> *     every second repeatedly, it&#39;s fine; it it&#39;s packet pacing that must sensitively fire near the resolution limit</span></div>
<div class="line"><a id="l00123" name="l00123"></a><span class="lineno">  123</span><span class="comment"> *     of the native #Timer facility, it *might* not be fine, and it&#39;s safer to use #Timer repeatedly.</span></div>
<div class="line"><a id="l00124" name="l00124"></a><span class="lineno">  124</span><span class="comment"> * - A #Timer can be re-scheduled to fire at an arbitrary different time than originally set.  We provide no such</span></div>
<div class="line"><a id="l00125" name="l00125"></a><span class="lineno">  125</span><span class="comment"> *   facility.  (We could provide such an API at the cost of API and implementation complexity; it&#39;s a judgment call,</span></div>
<div class="line"><a id="l00126" name="l00126"></a><span class="lineno">  126</span><span class="comment"> *   but I feel at that point just use a #Timer.)</span></div>
<div class="line"><a id="l00127" name="l00127"></a><span class="lineno">  127</span><span class="comment"> *   - However, we provide one special case of this: the timer can be fired</span></div>
<div class="line"><a id="l00128" name="l00128"></a><span class="lineno">  128</span><span class="comment"> *     ASAP, a/k/a short-fired, via scheduled_task_short_fire().</span></div>
<div class="line"><a id="l00129" name="l00129"></a><span class="lineno">  129</span><span class="comment"> * - One can (incrementally) schedule 2+ tasks to fire at the scheduled time on one #Timer; this facility only takes</span></div>
<div class="line"><a id="l00130" name="l00130"></a><span class="lineno">  130</span><span class="comment"> *   exactly 1 task, up-front. (We could provide such an API, but again this feels like it defeats the point.)</span></div>
<div class="line"><a id="l00131" name="l00131"></a><span class="lineno">  131</span><span class="comment"> * - #Timer has certain informational accessors (like one that returns the scheduled firing time) that we lack.</span></div>
<div class="line"><a id="l00132" name="l00132"></a><span class="lineno">  132</span><span class="comment"> *   (Again, we could provide this also -- but why?)</span></div>
<div class="line"><a id="l00133" name="l00133"></a><span class="lineno">  133</span><span class="comment"> *</span></div>
<div class="line"><a id="l00134" name="l00134"></a><span class="lineno">  134</span><span class="comment"> * @todo We could eliminate schedule_task_from_now() potential limitation versus #Timer wherein each call constructs</span></div>
<div class="line"><a id="l00135" name="l00135"></a><span class="lineno">  135</span><span class="comment"> * (internally) a new #Timer.  A pool of `Timer`s can be internally maintained to implement this.  This may or may not</span></div>
<div class="line"><a id="l00136" name="l00136"></a><span class="lineno">  136</span><span class="comment"> * be worth the complexity, but if the API can remain identically simple while cleanly eliminating the one perf-related</span></div>
<div class="line"><a id="l00137" name="l00137"></a><span class="lineno">  137</span><span class="comment"> * reason to choose #Timer over this simpler facility, then that is a clean win from the API user&#39;s point of view.</span></div>
<div class="line"><a id="l00138" name="l00138"></a><span class="lineno">  138</span><span class="comment"> * By comparison, other possible improvements mentioned *complicate* the API which makes them less attractive.</span></div>
<div class="line"><a id="l00139" name="l00139"></a><span class="lineno">  139</span><span class="comment"> *</span></div>
<div class="line"><a id="l00140" name="l00140"></a><span class="lineno">  140</span><span class="comment"> * @see util::Timer doc header for native #Timer resolution limitations (which apply to quite-low `from_now` values).</span></div>
<div class="line"><a id="l00141" name="l00141"></a><span class="lineno">  141</span><span class="comment"> * @note Design note: This is a small, somewhat C-style set of functions -- C-style in that it returns a handle</span></div>
<div class="line"><a id="l00142" name="l00142"></a><span class="lineno">  142</span><span class="comment"> *       on which to potentially call more functions as opposed to just being a class with methods.  This is</span></div>
<div class="line"><a id="l00143" name="l00143"></a><span class="lineno">  143</span><span class="comment"> *       intentional, because #Timer already provides the stateful `class`.  The picture is slightly muddled because</span></div>
<div class="line"><a id="l00144" name="l00144"></a><span class="lineno">  144</span><span class="comment"> *       we DO provide some &quot;methods&quot; -- so why not make it a `class` after all, just a simpler one than #Timer?</span></div>
<div class="line"><a id="l00145" name="l00145"></a><span class="lineno">  145</span><span class="comment"> *       Answer: I believe this keeps the API simple: Step 1: Schedule it. Step 2 (optional): Short-fire or cancel it.</span></div>
<div class="line"><a id="l00146" name="l00146"></a><span class="lineno">  146</span><span class="comment"> *       There are no corner cases introduced as might have been via increased potential statefulness inherent with a</span></div>
<div class="line"><a id="l00147" name="l00147"></a><span class="lineno">  147</span><span class="comment"> *       class.  But see the following to-do.</span></div>
<div class="line"><a id="l00148" name="l00148"></a><span class="lineno">  148</span><span class="comment"> *</span></div>
<div class="line"><a id="l00149" name="l00149"></a><span class="lineno">  149</span><span class="comment"> * @todo schedule_task_from_now() and surrounding API provides an easy way to schedule a thing into the future, but</span></div>
<div class="line"><a id="l00150" name="l00150"></a><span class="lineno">  150</span><span class="comment"> * it is built on top of boost.asio util::Timer directly; an intermediate wrapper class around this would be quite</span></div>
<div class="line"><a id="l00151" name="l00151"></a><span class="lineno">  151</span><span class="comment"> * useful in its own right so that all boost.asio features including its perf-friendliness would be retained along</span></div>
<div class="line"><a id="l00152" name="l00152"></a><span class="lineno">  152</span><span class="comment"> * with eliminating its annoyances (around canceling-but-not-really and similar).  Then scheduled_task_from_now()</span></div>
<div class="line"><a id="l00153" name="l00153"></a><span class="lineno">  153</span><span class="comment"> * would be internally even simpler, while a non-annoying util::Timer would become available for more advanced use</span></div>
<div class="line"><a id="l00154" name="l00154"></a><span class="lineno">  154</span><span class="comment"> * cases.  echan may have such a class (in a different project) ready to adapt (called `Serial_task_timer`).</span></div>
<div class="line"><a id="l00155" name="l00155"></a><span class="lineno">  155</span><span class="comment"> * I believe it internally uses integer &quot;task ID&quot; to distinguish between scheduled tasks issued in some chronological</span></div>
<div class="line"><a id="l00156" name="l00156"></a><span class="lineno">  156</span><span class="comment"> * order, so that boost.asio firing a task after it has been canceled/pre-fired can be easily detected.</span></div>
<div class="line"><a id="l00157" name="l00157"></a><span class="lineno">  157</span><span class="comment"> *</span></div>
<div class="line"><a id="l00158" name="l00158"></a><span class="lineno">  158</span><span class="comment"> * @param logger_ptr</span></div>
<div class="line"><a id="l00159" name="l00159"></a><span class="lineno">  159</span><span class="comment"> *        Logging, if any -- including in the background -- will be done via this logger.</span></div>
<div class="line"><a id="l00160" name="l00160"></a><span class="lineno">  160</span><span class="comment"> * @param from_now</span></div>
<div class="line"><a id="l00161" name="l00161"></a><span class="lineno">  161</span><span class="comment"> *        Fire ASAP once this time period passes (0 to fire ASAP).  A negative value has the same effect as 0.</span></div>
<div class="line"><a id="l00162" name="l00162"></a><span class="lineno">  162</span><span class="comment"> * @param single_threaded</span></div>
<div class="line"><a id="l00163" name="l00163"></a><span class="lineno">  163</span><span class="comment"> *        Set to a true value if and only if, basically, `*task_engine` is single-threaded, and you promise not</span></div>
<div class="line"><a id="l00164" name="l00164"></a><span class="lineno">  164</span><span class="comment"> *        to call anything on the returned `Scheduled_task_handle` except from that same thread.  More formally, see</span></div>
<div class="line"><a id="l00165" name="l00165"></a><span class="lineno">  165</span><span class="comment"> *        above.</span></div>
<div class="line"><a id="l00166" name="l00166"></a><span class="lineno">  166</span><span class="comment"> * @param task_engine</span></div>
<div class="line"><a id="l00167" name="l00167"></a><span class="lineno">  167</span><span class="comment"> *        The `Task_engine` onto which the given task may be `post()`ed (or equivalent).</span></div>
<div class="line"><a id="l00168" name="l00168"></a><span class="lineno">  168</span><span class="comment"> * @param task_body_moved</span></div>
<div class="line"><a id="l00169" name="l00169"></a><span class="lineno">  169</span><span class="comment"> *        The task to execute within `*task_engine` unless successfully canceled.  See template param doc below also</span></div>
<div class="line"><a id="l00170" name="l00170"></a><span class="lineno">  170</span><span class="comment"> *        regarding `Strand` and other executor binding.</span></div>
<div class="line"><a id="l00171" name="l00171"></a><span class="lineno">  171</span><span class="comment"> * @return Handle to the scheduled task which can be ignored in most cases.  If you want to cancel, short-fire, etc.</span></div>
<div class="line"><a id="l00172" name="l00172"></a><span class="lineno">  172</span><span class="comment"> *         subsequently, save this (by value) and operate on it subsequently, e.g., with scheduled_task_cancel().</span></div>
<div class="line"><a id="l00173" name="l00173"></a><span class="lineno">  173</span><span class="comment"> *</span></div>
<div class="line"><a id="l00174" name="l00174"></a><span class="lineno">  174</span><span class="comment"> * @tparam Scheduled_task_handler</span></div>
<div class="line"><a id="l00175" name="l00175"></a><span class="lineno">  175</span><span class="comment"> *         Completion handler with signature compatible with `void (bool short_fired)`.</span></div>
<div class="line"><a id="l00176" name="l00176"></a><span class="lineno">  176</span><span class="comment"> *         This allows for standard boost.asio semantics, including associating with an executor such as a</span></div>
<div class="line"><a id="l00177" name="l00177"></a><span class="lineno">  177</span><span class="comment"> *         `boost::asio::io_context::strand`.  In particular you may pass in: `bind_executor(S, F)`, where</span></div>
<div class="line"><a id="l00178" name="l00178"></a><span class="lineno">  178</span><span class="comment"> *         `F(bool short_fire)` is the handler, and `S` is a #Strand (or other executor).</span></div>
<div class="line"><a id="l00179" name="l00179"></a><span class="lineno">  179</span><span class="comment"> *         Binding to a #Strand will ensure the fired or short-fired body will not execute concurrently with</span></div>
<div class="line"><a id="l00180" name="l00180"></a><span class="lineno">  180</span><span class="comment"> *         any other handler also bound to it.</span></div>
<div class="line"><a id="l00181" name="l00181"></a><span class="lineno">  181</span><span class="comment"> */</span></div>
<div class="line"><a id="l00182" name="l00182"></a><span class="lineno">  182</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> Scheduled_task_handler&gt;</div>
<div class="line"><a id="l00183" name="l00183"></a><span class="lineno">  183</span><a class="code hl_typedef" href="namespaceflow_1_1util.html#aa0d10f5a906b3229f48979aa43e9ff7e">Scheduled_task_handle</a> <a class="code hl_function" href="namespaceflow_1_1util.html#a74d4a66fb00055be4e1bd6ee98e04667">schedule_task_from_now</a>(<a class="code hl_class" href="classflow_1_1log_1_1Logger.html">log::Logger</a>* logger_ptr,</div>
<div class="line"><a id="l00184" name="l00184"></a><span class="lineno">  184</span>                                             <span class="keyword">const</span> <a class="code hl_typedef" href="namespaceflow.html#a48799f1263cdeedec125be51a3db2b79">Fine_duration</a>&amp; from_now, <span class="keywordtype">bool</span> single_threaded,</div>
<div class="line"><a id="l00185" name="l00185"></a><span class="lineno">  185</span>                                             <a class="code hl_typedef" href="namespaceflow_1_1util.html#ac3e89a8a271b0ddc76ac2a0ce488dea4">Task_engine</a>* task_engine,</div>
<div class="line"><a id="l00186" name="l00186"></a><span class="lineno">  186</span>                                             Scheduled_task_handler&amp;&amp; task_body_moved);</div>
<div class="line"><a id="l00187" name="l00187"></a><span class="lineno">  187</span><span class="comment"></span> </div>
<div class="line"><a id="l00188" name="l00188"></a><span class="lineno">  188</span><span class="comment">/**</span></div>
<div class="line"><a id="l00189" name="l00189"></a><span class="lineno">  189</span><span class="comment"> * Identical to schedule_task_from_now() except the time is specified in absolute terms.</span></div>
<div class="line"><a id="l00190" name="l00190"></a><span class="lineno">  190</span><span class="comment"> *</span></div>
<div class="line"><a id="l00191" name="l00191"></a><span class="lineno">  191</span><span class="comment"> * ### Performance note ###</span></div>
<div class="line"><a id="l00192" name="l00192"></a><span class="lineno">  192</span><span class="comment"> * The current implementation is such that there is no performance benefit to using</span></div>
<div class="line"><a id="l00193" name="l00193"></a><span class="lineno">  193</span><span class="comment"> * `schedule_task_from_now(at - Fine_clock::now(), ...)` over `schedule_task_at(at, ...)`.  Therefore, if it</span></div>
<div class="line"><a id="l00194" name="l00194"></a><span class="lineno">  194</span><span class="comment"> * is convenient for caller&#39;s code reuse to do the former, there is no perf downside to it, so feel free.</span></div>
<div class="line"><a id="l00195" name="l00195"></a><span class="lineno">  195</span><span class="comment"> *</span></div>
<div class="line"><a id="l00196" name="l00196"></a><span class="lineno">  196</span><span class="comment"> * @internal</span></div>
<div class="line"><a id="l00197" name="l00197"></a><span class="lineno">  197</span><span class="comment"> * ### Maintenance reminder ###</span></div>
<div class="line"><a id="l00198" name="l00198"></a><span class="lineno">  198</span><span class="comment"> * Ensure the &quot;Performance note&quot; is accurate w/r/t to the body of the function; as of this writing it is; keep</span></div>
<div class="line"><a id="l00199" name="l00199"></a><span class="lineno">  199</span><span class="comment"> * the two places in sync with each other.</span></div>
<div class="line"><a id="l00200" name="l00200"></a><span class="lineno">  200</span><span class="comment"> * @endinternal</span></div>
<div class="line"><a id="l00201" name="l00201"></a><span class="lineno">  201</span><span class="comment"> *</span></div>
<div class="line"><a id="l00202" name="l00202"></a><span class="lineno">  202</span><span class="comment"> * @param logger_ptr</span></div>
<div class="line"><a id="l00203" name="l00203"></a><span class="lineno">  203</span><span class="comment"> *        See schedule_task_from_now().</span></div>
<div class="line"><a id="l00204" name="l00204"></a><span class="lineno">  204</span><span class="comment"> * @param at</span></div>
<div class="line"><a id="l00205" name="l00205"></a><span class="lineno">  205</span><span class="comment"> *        Fire at this absolute time.  If this is in the past, it will fire ASAP.</span></div>
<div class="line"><a id="l00206" name="l00206"></a><span class="lineno">  206</span><span class="comment"> * @param single_threaded</span></div>
<div class="line"><a id="l00207" name="l00207"></a><span class="lineno">  207</span><span class="comment"> *        See schedule_task_from_now().</span></div>
<div class="line"><a id="l00208" name="l00208"></a><span class="lineno">  208</span><span class="comment"> * @param task_engine</span></div>
<div class="line"><a id="l00209" name="l00209"></a><span class="lineno">  209</span><span class="comment"> *        See schedule_task_from_now().</span></div>
<div class="line"><a id="l00210" name="l00210"></a><span class="lineno">  210</span><span class="comment"> * @param task_body_moved</span></div>
<div class="line"><a id="l00211" name="l00211"></a><span class="lineno">  211</span><span class="comment"> *        See schedule_task_from_now().</span></div>
<div class="line"><a id="l00212" name="l00212"></a><span class="lineno">  212</span><span class="comment"> * @return See schedule_task_from_now().</span></div>
<div class="line"><a id="l00213" name="l00213"></a><span class="lineno">  213</span><span class="comment"> *</span></div>
<div class="line"><a id="l00214" name="l00214"></a><span class="lineno">  214</span><span class="comment"> * @tparam Scheduled_task_handler</span></div>
<div class="line"><a id="l00215" name="l00215"></a><span class="lineno">  215</span><span class="comment"> *         See schedule_task_from_now().</span></div>
<div class="line"><a id="l00216" name="l00216"></a><span class="lineno">  216</span><span class="comment"> */</span></div>
<div class="line"><a id="l00217" name="l00217"></a><span class="lineno">  217</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> Scheduled_task_handler&gt;</div>
<div class="line"><a id="l00218" name="l00218"></a><span class="lineno">  218</span><a class="code hl_typedef" href="namespaceflow_1_1util.html#aa0d10f5a906b3229f48979aa43e9ff7e">Scheduled_task_handle</a> <a class="code hl_function" href="namespaceflow_1_1util.html#aad8c8f7335eb892350dc386cb4be397e">schedule_task_at</a>(<a class="code hl_class" href="classflow_1_1log_1_1Logger.html">log::Logger</a>* logger_ptr,</div>
<div class="line"><a id="l00219" name="l00219"></a><span class="lineno">  219</span>                                       <span class="keyword">const</span> <a class="code hl_typedef" href="namespaceflow.html#a9d9cc2eeb10d398cff5591d446b763b8">Fine_time_pt</a>&amp; at, <span class="keywordtype">bool</span> single_threaded,</div>
<div class="line"><a id="l00220" name="l00220"></a><span class="lineno">  220</span>                                       <a class="code hl_typedef" href="namespaceflow_1_1util.html#ac3e89a8a271b0ddc76ac2a0ce488dea4">Task_engine</a>* task_engine,</div>
<div class="line"><a id="l00221" name="l00221"></a><span class="lineno">  221</span>                                       Scheduled_task_handler&amp;&amp; task_body_moved);</div>
<div class="line"><a id="l00222" name="l00222"></a><span class="lineno">  222</span><span class="comment"></span> </div>
<div class="line"><a id="l00223" name="l00223"></a><span class="lineno">  223</span><span class="comment">/**</span></div>
<div class="line"><a id="l00224" name="l00224"></a><span class="lineno">  224</span><span class="comment"> * Attempts to reschedule a previously scheduled (by schedule_task_from_now() or similar) task to fire immediately.</span></div>
<div class="line"><a id="l00225" name="l00225"></a><span class="lineno">  225</span><span class="comment"> * For semantics, in the context of the entire facility, see schedule_task_from_now() doc header.</span></div>
<div class="line"><a id="l00226" name="l00226"></a><span class="lineno">  226</span><span class="comment"> *</span></div>
<div class="line"><a id="l00227" name="l00227"></a><span class="lineno">  227</span><span class="comment"> * @param logger_ptr</span></div>
<div class="line"><a id="l00228" name="l00228"></a><span class="lineno">  228</span><span class="comment"> *        See schedule_task_from_now().</span></div>
<div class="line"><a id="l00229" name="l00229"></a><span class="lineno">  229</span><span class="comment"> * @param task</span></div>
<div class="line"><a id="l00230" name="l00230"></a><span class="lineno">  230</span><span class="comment"> *        (Copy of) the handle returned by a previous `schedule_task_*()` call.</span></div>
<div class="line"><a id="l00231" name="l00231"></a><span class="lineno">  231</span><span class="comment"> * @return `true` if the task will indeed have executed soon with `short_fire == true`.</span></div>
<div class="line"><a id="l00232" name="l00232"></a><span class="lineno">  232</span><span class="comment"> *         `false` if it has or will soon have executed with `short_file == false`; or if it has already been</span></div>
<div class="line"><a id="l00233" name="l00233"></a><span class="lineno">  233</span><span class="comment"> *         successfully canceled via scheduled_task_cancel().</span></div>
<div class="line"><a id="l00234" name="l00234"></a><span class="lineno">  234</span><span class="comment"> */</span></div>
<div class="line"><a id="l00235" name="l00235"></a><span class="lineno">  235</span><span class="keywordtype">bool</span> <a class="code hl_function" href="namespaceflow_1_1util.html#abe8d04de7ba9ac770112ee585b77cd20">scheduled_task_short_fire</a>(<a class="code hl_class" href="classflow_1_1log_1_1Logger.html">log::Logger</a>* logger_ptr, <a class="code hl_typedef" href="namespaceflow_1_1util.html#aa0d10f5a906b3229f48979aa43e9ff7e">Scheduled_task_handle</a> task);</div>
<div class="line"><a id="l00236" name="l00236"></a><span class="lineno">  236</span><span class="comment"></span> </div>
<div class="line"><a id="l00237" name="l00237"></a><span class="lineno">  237</span><span class="comment">/**</span></div>
<div class="line"><a id="l00238" name="l00238"></a><span class="lineno">  238</span><span class="comment"> * Attempts to prevent the execution of a previously scheduled (by schedule_task_from_now() or similar) task.</span></div>
<div class="line"><a id="l00239" name="l00239"></a><span class="lineno">  239</span><span class="comment"> * For semantics, in the context of the entire facility, see schedule_task_from_now() doc header.</span></div>
<div class="line"><a id="l00240" name="l00240"></a><span class="lineno">  240</span><span class="comment"> *</span></div>
<div class="line"><a id="l00241" name="l00241"></a><span class="lineno">  241</span><span class="comment"> * @param logger_ptr</span></div>
<div class="line"><a id="l00242" name="l00242"></a><span class="lineno">  242</span><span class="comment"> *        See scheduled_task_short_fire().</span></div>
<div class="line"><a id="l00243" name="l00243"></a><span class="lineno">  243</span><span class="comment"> * @param task</span></div>
<div class="line"><a id="l00244" name="l00244"></a><span class="lineno">  244</span><span class="comment"> *        See scheduled_task_short_fire().</span></div>
<div class="line"><a id="l00245" name="l00245"></a><span class="lineno">  245</span><span class="comment"> * @return `true` if the task has not executed and will NEVER have executed, AND no other scheduled_task_cancel()</span></div>
<div class="line"><a id="l00246" name="l00246"></a><span class="lineno">  246</span><span class="comment"> *         with the same arg has succeeded before this.</span></div>
<div class="line"><a id="l00247" name="l00247"></a><span class="lineno">  247</span><span class="comment"> *         `false` if it has or will soon have executed because the present call occurred too late to stop it.</span></div>
<div class="line"><a id="l00248" name="l00248"></a><span class="lineno">  248</span><span class="comment"> *         Namely, it may have fired or short-fired already.</span></div>
<div class="line"><a id="l00249" name="l00249"></a><span class="lineno">  249</span><span class="comment"> */</span></div>
<div class="line"><a id="l00250" name="l00250"></a><span class="lineno">  250</span><span class="keywordtype">bool</span> <a class="code hl_function" href="namespaceflow_1_1util.html#ad92e68a1b22556f2625292098c0036a2">scheduled_task_cancel</a>(<a class="code hl_class" href="classflow_1_1log_1_1Logger.html">log::Logger</a>* logger_ptr, <a class="code hl_typedef" href="namespaceflow_1_1util.html#aa0d10f5a906b3229f48979aa43e9ff7e">Scheduled_task_handle</a> task);</div>
<div class="line"><a id="l00251" name="l00251"></a><span class="lineno">  251</span><span class="comment"></span> </div>
<div class="line"><a id="l00252" name="l00252"></a><span class="lineno">  252</span><span class="comment">/**</span></div>
<div class="line"><a id="l00253" name="l00253"></a><span class="lineno">  253</span><span class="comment"> * Returns how long remains until a previously scheduled (by schedule_task_from_now() or similar) task fires;</span></div>
<div class="line"><a id="l00254" name="l00254"></a><span class="lineno">  254</span><span class="comment"> * or negative time if that point is in the past; or special value if the task has been canceled.</span></div>
<div class="line"><a id="l00255" name="l00255"></a><span class="lineno">  255</span><span class="comment"> *</span></div>
<div class="line"><a id="l00256" name="l00256"></a><span class="lineno">  256</span><span class="comment"> * This is based solely on what was specified when scheduling it; it may be different from when it will actually fire</span></div>
<div class="line"><a id="l00257" name="l00257"></a><span class="lineno">  257</span><span class="comment"> * or has fired.  However, a special value (see below) is returned, if the task has been canceled</span></div>
<div class="line"><a id="l00258" name="l00258"></a><span class="lineno">  258</span><span class="comment"> * (scheduled_task_cancel()).</span></div>
<div class="line"><a id="l00259" name="l00259"></a><span class="lineno">  259</span><span class="comment"> *</span></div>
<div class="line"><a id="l00260" name="l00260"></a><span class="lineno">  260</span><span class="comment"> * @param logger_ptr</span></div>
<div class="line"><a id="l00261" name="l00261"></a><span class="lineno">  261</span><span class="comment"> *        Logging, if any, will be done synchronously via this logger.</span></div>
<div class="line"><a id="l00262" name="l00262"></a><span class="lineno">  262</span><span class="comment"> * @param task</span></div>
<div class="line"><a id="l00263" name="l00263"></a><span class="lineno">  263</span><span class="comment"> *        (Copy of) the handle returned by a previous `schedule_task_*()` call.</span></div>
<div class="line"><a id="l00264" name="l00264"></a><span class="lineno">  264</span><span class="comment"> * @return Positive duration if it is set to fire in the future; negative or zero duration otherwise; or</span></div>
<div class="line"><a id="l00265" name="l00265"></a><span class="lineno">  265</span><span class="comment"> *         special value `Fine_duration::max()` to indicate the task has been canceled.</span></div>
<div class="line"><a id="l00266" name="l00266"></a><span class="lineno">  266</span><span class="comment"> *         Note a non-`max()` (probably negative) duration will be returned even if it has already fired.</span></div>
<div class="line"><a id="l00267" name="l00267"></a><span class="lineno">  267</span><span class="comment"> */</span></div>
<div class="line"><a id="l00268" name="l00268"></a><span class="lineno">  268</span><a class="code hl_typedef" href="namespaceflow.html#a48799f1263cdeedec125be51a3db2b79">Fine_duration</a> <a class="code hl_function" href="namespaceflow_1_1util.html#a9a0812b36dc401a3b2ac5e60e2a070d0">scheduled_task_fires_from_now_or_canceled</a>(<a class="code hl_class" href="classflow_1_1log_1_1Logger.html">log::Logger</a>* logger_ptr, <a class="code hl_typedef" href="namespaceflow_1_1util.html#add471ec4a0f0b76793c9c84adb4916d5">Scheduled_task_const_handle</a> task);</div>
<div class="line"><a id="l00269" name="l00269"></a><span class="lineno">  269</span><span class="comment"></span> </div>
<div class="line"><a id="l00270" name="l00270"></a><span class="lineno">  270</span><span class="comment">/**</span></div>
<div class="line"><a id="l00271" name="l00271"></a><span class="lineno">  271</span><span class="comment"> * Returns whether a previously scheduled (by schedule_task_from_now() or similar) task has already fired.</span></div>
<div class="line"><a id="l00272" name="l00272"></a><span class="lineno">  272</span><span class="comment"> * Note that this cannot be `true` while scheduled_task_canceled() is `false` and vice versa (but see thread safety note</span></div>
<div class="line"><a id="l00273" name="l00273"></a><span class="lineno">  273</span><span class="comment"> * below).</span></div>
<div class="line"><a id="l00274" name="l00274"></a><span class="lineno">  274</span><span class="comment"> *</span></div>
<div class="line"><a id="l00275" name="l00275"></a><span class="lineno">  275</span><span class="comment"> * Also note that, while thread-safe, if `!single_threaded` in the original scheduling call, then the value</span></div>
<div class="line"><a id="l00276" name="l00276"></a><span class="lineno">  276</span><span class="comment"> * returned might be different even if checked immediately after this function exits, in the same thread.</span></div>
<div class="line"><a id="l00277" name="l00277"></a><span class="lineno">  277</span><span class="comment"> * However, if `single_threaded` (and one indeed properly uses `task` from one thread only) then it is guaranteed</span></div>
<div class="line"><a id="l00278" name="l00278"></a><span class="lineno">  278</span><span class="comment"> * this value is consistent/correct synchronously in the caller&#39;s thread, until code in that thread actively changes it</span></div>
<div class="line"><a id="l00279" name="l00279"></a><span class="lineno">  279</span><span class="comment"> * (e.g., by canceling task).</span></div>
<div class="line"><a id="l00280" name="l00280"></a><span class="lineno">  280</span><span class="comment"> *</span></div>
<div class="line"><a id="l00281" name="l00281"></a><span class="lineno">  281</span><span class="comment"> * @param logger_ptr</span></div>
<div class="line"><a id="l00282" name="l00282"></a><span class="lineno">  282</span><span class="comment"> *        See scheduled_task_fires_from_now_or_canceled().</span></div>
<div class="line"><a id="l00283" name="l00283"></a><span class="lineno">  283</span><span class="comment"> * @param task</span></div>
<div class="line"><a id="l00284" name="l00284"></a><span class="lineno">  284</span><span class="comment"> *        See scheduled_task_fires_from_now_or_canceled().</span></div>
<div class="line"><a id="l00285" name="l00285"></a><span class="lineno">  285</span><span class="comment"> * @return See above.</span></div>
<div class="line"><a id="l00286" name="l00286"></a><span class="lineno">  286</span><span class="comment"> */</span></div>
<div class="line"><a id="l00287" name="l00287"></a><span class="lineno">  287</span><span class="keywordtype">bool</span> <a class="code hl_function" href="namespaceflow_1_1util.html#a79a0f182b38898771d669475d3e963a4">scheduled_task_fired</a>(<a class="code hl_class" href="classflow_1_1log_1_1Logger.html">log::Logger</a>* logger_ptr, <a class="code hl_typedef" href="namespaceflow_1_1util.html#add471ec4a0f0b76793c9c84adb4916d5">Scheduled_task_const_handle</a> task);</div>
<div class="line"><a id="l00288" name="l00288"></a><span class="lineno">  288</span><span class="comment"></span> </div>
<div class="line"><a id="l00289" name="l00289"></a><span class="lineno">  289</span><span class="comment">/**</span></div>
<div class="line"><a id="l00290" name="l00290"></a><span class="lineno">  290</span><span class="comment"> * Returns whether a previously scheduled (by schedule_task_from_now() or similar) task has been canceled.</span></div>
<div class="line"><a id="l00291" name="l00291"></a><span class="lineno">  291</span><span class="comment"> * Note that this cannot be `true` while scheduled_task_fired() is `false` and vice versa (but see thread safety note</span></div>
<div class="line"><a id="l00292" name="l00292"></a><span class="lineno">  292</span><span class="comment"> * below).</span></div>
<div class="line"><a id="l00293" name="l00293"></a><span class="lineno">  293</span><span class="comment"> *</span></div>
<div class="line"><a id="l00294" name="l00294"></a><span class="lineno">  294</span><span class="comment"> * Thread safety notes in the scheduled_task_fired() doc header apply equally here.</span></div>
<div class="line"><a id="l00295" name="l00295"></a><span class="lineno">  295</span><span class="comment"> *</span></div>
<div class="line"><a id="l00296" name="l00296"></a><span class="lineno">  296</span><span class="comment"> * @param logger_ptr</span></div>
<div class="line"><a id="l00297" name="l00297"></a><span class="lineno">  297</span><span class="comment"> *        See scheduled_task_fired().</span></div>
<div class="line"><a id="l00298" name="l00298"></a><span class="lineno">  298</span><span class="comment"> * @param task</span></div>
<div class="line"><a id="l00299" name="l00299"></a><span class="lineno">  299</span><span class="comment"> *        See scheduled_task_fired().</span></div>
<div class="line"><a id="l00300" name="l00300"></a><span class="lineno">  300</span><span class="comment"> * @return See above.</span></div>
<div class="line"><a id="l00301" name="l00301"></a><span class="lineno">  301</span><span class="comment"> */</span></div>
<div class="line"><a id="l00302" name="l00302"></a><span class="lineno">  302</span><span class="keywordtype">bool</span> <a class="code hl_function" href="namespaceflow_1_1util.html#ad339cf2543e0ad692203817b19e4e8ed">scheduled_task_canceled</a>(<a class="code hl_class" href="classflow_1_1log_1_1Logger.html">log::Logger</a>* logger_ptr, <a class="code hl_typedef" href="namespaceflow_1_1util.html#add471ec4a0f0b76793c9c84adb4916d5">Scheduled_task_const_handle</a> task);</div>
<div class="line"><a id="l00303" name="l00303"></a><span class="lineno">  303</span> </div>
<div class="line"><a id="l00304" name="l00304"></a><span class="lineno">  304</span>} <span class="comment">// namespace flow::util</span></div>
<div class="ttc" id="aclassflow_1_1Function_html"><div class="ttname"><a href="classflow_1_1Function.html">flow::Function</a></div><div class="ttdef"><b>Definition:</b> <a href="common_8hpp_source.html#l00512">common.hpp:512</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Logger_html"><div class="ttname"><a href="classflow_1_1log_1_1Logger.html">flow::log::Logger</a></div><div class="ttdoc">Interface that the user should implement, passing the implementing Logger into logging classes (Flow'...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01280">log.hpp:1284</a></div></div>
<div class="ttc" id="alog__fwd_8hpp_html"><div class="ttname"><a href="log__fwd_8hpp.html">log_fwd.hpp</a></div></div>
<div class="ttc" id="anamespaceflow_1_1util_html"><div class="ttname"><a href="namespaceflow_1_1util.html">flow::util</a></div><div class="ttdoc">Flow module containing miscellaneous general-use facilities that don't fit into any other Flow module...</div><div class="ttdef"><b>Definition:</b> <a href="basic__blob_8hpp_source.html#l00028">basic_blob.hpp:29</a></div></div>
<div class="ttc" id="anamespaceflow_1_1util_html_a74d4a66fb00055be4e1bd6ee98e04667"><div class="ttname"><a href="namespaceflow_1_1util.html#a74d4a66fb00055be4e1bd6ee98e04667">flow::util::schedule_task_from_now</a></div><div class="ttdeci">Scheduled_task_handle schedule_task_from_now(log::Logger *logger_ptr, const Fine_duration &amp;from_now, bool single_threaded, Task_engine *task_engine, Scheduled_task_handler &amp;&amp;task_body_moved)</div><div class="ttdoc">Schedule the given function to execute in a certain amount of time: A handy wrapper around Timer (asi...</div><div class="ttdef"><b>Definition:</b> <a href="sched__task_8hpp_source.html#l00034">sched_task.hpp:34</a></div></div>
<div class="ttc" id="anamespaceflow_1_1util_html_a79a0f182b38898771d669475d3e963a4"><div class="ttname"><a href="namespaceflow_1_1util.html#a79a0f182b38898771d669475d3e963a4">flow::util::scheduled_task_fired</a></div><div class="ttdeci">bool scheduled_task_fired(log::Logger *logger_ptr, Scheduled_task_const_handle task)</div><div class="ttdoc">Returns whether a previously scheduled (by schedule_task_from_now() or similar) task has already fire...</div><div class="ttdef"><b>Definition:</b> <a href="sched__task_8cpp_source.html#l00238">sched_task.cpp:238</a></div></div>
<div class="ttc" id="anamespaceflow_1_1util_html_a9a0812b36dc401a3b2ac5e60e2a070d0"><div class="ttname"><a href="namespaceflow_1_1util.html#a9a0812b36dc401a3b2ac5e60e2a070d0">flow::util::scheduled_task_fires_from_now_or_canceled</a></div><div class="ttdeci">Fine_duration scheduled_task_fires_from_now_or_canceled(log::Logger *logger_ptr, Scheduled_task_const_handle task)</div><div class="ttdoc">Returns how long remains until a previously scheduled (by schedule_task_from_now() or similar) task f...</div><div class="ttdef"><b>Definition:</b> <a href="sched__task_8cpp_source.html#l00200">sched_task.cpp:200</a></div></div>
<div class="ttc" id="anamespaceflow_1_1util_html_aa0d10f5a906b3229f48979aa43e9ff7e"><div class="ttname"><a href="namespaceflow_1_1util.html#aa0d10f5a906b3229f48979aa43e9ff7e">flow::util::Scheduled_task_handle</a></div><div class="ttdeci">boost::shared_ptr&lt; Scheduled_task_handle_state &gt; Scheduled_task_handle</div><div class="ttdoc">Black-box type that represents a handle to a scheduled task as scheduled by schedule_task_at() or sch...</div><div class="ttdef"><b>Definition:</b> <a href="sched__task__fwd_8hpp_source.html#l00045">sched_task_fwd.hpp:45</a></div></div>
<div class="ttc" id="anamespaceflow_1_1util_html_aad8c8f7335eb892350dc386cb4be397e"><div class="ttname"><a href="namespaceflow_1_1util.html#aad8c8f7335eb892350dc386cb4be397e">flow::util::schedule_task_at</a></div><div class="ttdeci">Scheduled_task_handle schedule_task_at(log::Logger *logger_ptr, const Fine_time_pt &amp;at, bool single_threaded, Task_engine *task_engine, Scheduled_task_handler &amp;&amp;task_body_moved)</div><div class="ttdoc">Identical to schedule_task_from_now() except the time is specified in absolute terms.</div><div class="ttdef"><b>Definition:</b> <a href="sched__task_8hpp_source.html#l00245">sched_task.hpp:245</a></div></div>
<div class="ttc" id="anamespaceflow_1_1util_html_abe8d04de7ba9ac770112ee585b77cd20"><div class="ttname"><a href="namespaceflow_1_1util.html#abe8d04de7ba9ac770112ee585b77cd20">flow::util::scheduled_task_short_fire</a></div><div class="ttdeci">bool scheduled_task_short_fire(log::Logger *logger_ptr, Scheduled_task_handle task)</div><div class="ttdoc">Attempts to reschedule a previously scheduled (by schedule_task_from_now() or similar) task to fire i...</div><div class="ttdef"><b>Definition:</b> <a href="sched__task_8cpp_source.html#l00095">sched_task.cpp:95</a></div></div>
<div class="ttc" id="anamespaceflow_1_1util_html_ac3e89a8a271b0ddc76ac2a0ce488dea4"><div class="ttname"><a href="namespaceflow_1_1util.html#ac3e89a8a271b0ddc76ac2a0ce488dea4">flow::util::Task_engine</a></div><div class="ttdeci">boost::asio::io_context Task_engine</div><div class="ttdoc">Short-hand for boost.asio event service, the central class of boost.asio.</div><div class="ttdef"><b>Definition:</b> <a href="util__fwd_8hpp_source.html#l00135">util_fwd.hpp:135</a></div></div>
<div class="ttc" id="anamespaceflow_1_1util_html_ad339cf2543e0ad692203817b19e4e8ed"><div class="ttname"><a href="namespaceflow_1_1util.html#ad339cf2543e0ad692203817b19e4e8ed">flow::util::scheduled_task_canceled</a></div><div class="ttdeci">bool scheduled_task_canceled(log::Logger *logger_ptr, Scheduled_task_const_handle task)</div><div class="ttdoc">Returns whether a previously scheduled (by schedule_task_from_now() or similar) task has been cancele...</div><div class="ttdef"><b>Definition:</b> <a href="sched__task_8cpp_source.html#l00259">sched_task.cpp:259</a></div></div>
<div class="ttc" id="anamespaceflow_1_1util_html_ad92e68a1b22556f2625292098c0036a2"><div class="ttname"><a href="namespaceflow_1_1util.html#ad92e68a1b22556f2625292098c0036a2">flow::util::scheduled_task_cancel</a></div><div class="ttdeci">bool scheduled_task_cancel(log::Logger *logger_ptr, Scheduled_task_handle task)</div><div class="ttdoc">Attempts to prevent the execution of a previously scheduled (by schedule_task_from_now() or similar) ...</div><div class="ttdef"><b>Definition:</b> <a href="sched__task_8cpp_source.html#l00026">sched_task.cpp:26</a></div></div>
<div class="ttc" id="anamespaceflow_1_1util_html_add471ec4a0f0b76793c9c84adb4916d5"><div class="ttname"><a href="namespaceflow_1_1util.html#add471ec4a0f0b76793c9c84adb4916d5">flow::util::Scheduled_task_const_handle</a></div><div class="ttdeci">boost::shared_ptr&lt; const Scheduled_task_handle_state &gt; Scheduled_task_const_handle</div><div class="ttdoc">Equivalent to Scheduled_task_handle but refers to immutable version of a task.</div><div class="ttdef"><b>Definition:</b> <a href="sched__task__fwd_8hpp_source.html#l00052">sched_task_fwd.hpp:52</a></div></div>
<div class="ttc" id="anamespaceflow_html_a48799f1263cdeedec125be51a3db2b79"><div class="ttname"><a href="namespaceflow.html#a48799f1263cdeedec125be51a3db2b79">flow::Fine_duration</a></div><div class="ttdeci">Fine_clock::duration Fine_duration</div><div class="ttdoc">A high-res time duration as computed from two Fine_time_pts.</div><div class="ttdef"><b>Definition:</b> <a href="common_8hpp_source.html#l00416">common.hpp:416</a></div></div>
<div class="ttc" id="anamespaceflow_html_a9d9cc2eeb10d398cff5591d446b763b8"><div class="ttname"><a href="namespaceflow.html#a9d9cc2eeb10d398cff5591d446b763b8">flow::Fine_time_pt</a></div><div class="ttdeci">Fine_clock::time_point Fine_time_pt</div><div class="ttdoc">A high-res time point as returned by Fine_clock::now() and suitable for precise time math in general.</div><div class="ttdef"><b>Definition:</b> <a href="common_8hpp_source.html#l00413">common.hpp:413</a></div></div>
<div class="ttc" id="autil__fwd_8hpp_html"><div class="ttname"><a href="util__fwd_8hpp.html">util_fwd.hpp</a></div></div>
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